


Fullfill your promises!

by vanilladrops



Category: Shall We Date?: Obey Me!
Genre: Books, Eventual Smut, F/M, Fluff, Fluff and Smut, Oral Sex, Porn With Plot, Porn with Feelings, Possessive Behavior, Sex, Vaginal Sex
Language: English
Status: Completed
Published: 2020-04-03
Updated: 2020-04-12
Packaged: 2021-03-01 07:48:44
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 5
Words: 4,129
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23467909
Author URL: https://archiveofourown.org/users/vanilladrops/pseuds/vanilladrops
Summary: "She took a deep breath, anxious to, in one way or another, be filled by Satan.“You’re mine” he had said that morning, but now there he was, sitting on his desk, bending over a book and devouring it with his eyes."Satan had been a tease, but... why couldn't he fulfill his promises? And now they have to watch over Levi and Beel to make sure both would get on time for classes! Will he ever touch her?
Relationships: Main Character & Satan (Shall We Date?: Obey Me!), Satan (Shall We Date?: Obey Me!) & Reader, Satan (Shall We Date?: Obey Me!)/Original Female Character(s)
Comments: 22
Kudos: 208





	1. First Night

Satan’s bed smelled of him. It was a warm perfume that reminded her of her sunny days on the human world. Fresh apples, black tea and brand-new books. She took a deep breath, anxious to, in one way or another, be filled by Satan.

She looked at him from across the room. “ _You’re mine_ ” he had said that morning, but now there he was, sitting on his desk, bending over a book and devouring it with his eyes. He looked handsome; she had no problem in admitting that. The way his hair shone in gold against the candles, the elegant motion in which he passed pages, the soft pinkish color of his parted lips… all that made her shiver under his sheets, where disappointment built up in all those unfulfilled promises.

Resigned, and a bit jealous, she took another breath, aware that this was the only way for her to have Satan _inside_.

“Why must you be like that?” She mumbled, reminding herself of the many times Satan had said something dubious in front of his brothers. In front of… She held her breath. In front of Lucifer! Why, yes. Lucifer had always been present, and Satan knew he had taken a liking to her. So… She puffed her cheeks, suddenly bitter.

Levi, sleeping on the floor, moved a bit, kicking Beel on the leg. She had forgotten about their presence, and let her anger subdue a bit. Both Satan and her had been assigned to watch over those two. They were to make sure everyone would get enough to get on time for classes, so Satan’s brilliant idea was to have everyone in his room under his watch. She wouldn’t deny the excitement she felt when he had proposed it, imagining all sorts of naughty things to happen in his room. But, as she had soon realized, nothing was going to happen.

**Absolutely nothing.**

Satan, immersed on his reading, felt a wave of hostility coming into his direction. He was too accustomed to the feeling of wrath to actually care about it, but, as soon as he noticed _where_ it was coming from, he had to pause a bit and put his book down. Yes, as he had sensed, that demonic stare wasn’t coming from an actual demon, but from that human. She had just enough of her eyes peeking out of his bedsheet, staring at him in such a deadly way that even he, the avatar of wrath, shuddered.

He looked back at her and tilted his head a bit, wondering what had happened. She was to be sleeping, not staring at someone with such latent anger. Satan motioned in her direction, and she quickly hid under his sheets, thanking the darkness for not revealing her flushed cheeks. She had been trying to make up her mind about hating him but, as soon as he loosely tilted his head, she had to abandon that line of thought. He was too cute to be hated.

“What’s the matter?” Satan’s voice rang next to her. He sat on the edge of the bed and it cracked, making Levi mumble in his sleep.

“Satan…” She said in a slow voice, peeking from under the sheets. He stared at her, noticing the red cheeks, the small frown and those lovely teary eyes.

“ _Too cute!”_ He thought to himself, nodding when a flush overtook his own face. “Yes?”

But she did not answer. She didn’t have the guts to ask him to touch her, nor was her pride so untouchable that she didn’t fear a refusal. So, she just stared back at him, her eyes responding to the sudden awkwardness that overtook her.

“Well…” Satan puffed, feeling a tingle in his chest. She seemed so small in his bed, so fragile. Humans were too weak, and she was not an exception. He could break her if he wasn’t careful enough. Wrath wasn’t an easy thing to handle, and he was sure she wouldn’t be able to deal with its full force. So, he bent over her, as he had done countless times in the past, and blew in a low voice over her right ear: “…should I make you talk?”

Trapped in between his arms, she hoped that, this time, Satan would come forward and fulfill all those empty promises he had been making. But, as expectations built up inside her, she soon noticed that, again, he had just been teasing her.

“I know you won’t.” Her voice was sharp, dyed with the disappointment she felt. “Not unless Lucifer tells you to do so.”

Satan froze in place, and the sudden laugh that came from the floor seemed to make it all worse. They were not alone.

“LOL! That was an overkill!” Levi sang in delight, sitting right beside a still sleepy Beel. “I woke up to get some tickets for Mononoke Land’s midnight’s special event and… OMG. It’s just like that scene from ‘ _My Neighbor Is Hot But Not Manly Enough To Have His Way With Me, So I’ll Go And Have My Way With His Six Brothers’_! LOL!”

Satan did not answer. Dark clouds started to gather inside the room.

“That’s so lame!” Levi continued, unaware of the dangers awaiting him. “’LOL Mr. Perfect just got PWNED’ and… send! You know, Satan, I may be a shut-in, but you just got shut d-“

A pillow traveled through the room and hit Levi. Headshot. He stumbled back, screaming in pain, and a fight began. Beel woke up, and, still in a dazzle, got involved in the turmoil. In a matter of seconds, books were eaten, pillows were destroyed and bones may have been broken. Daylight came, and, once again, they were late for classes.


	2. First Morning

It was not until the next morning that the entire R.A.D. heard stories about what had happened to Satan’s room. Some would say that Cerberus itself had shown and eaten his books, others that his fight with Levi had opened a dimensional portal and that’s why part of his library had simply vanished. In spite of any rumor, though, Satan was now sitting in the front roll of the class with his most perfect smile drawn over his face.

“Scary.” Belphegor whispered, snuggling up to his favourite human in all Devildom. She nodded, felling ridiculously guilty over last night’s incident, and glanced over Satan’s direction. Belphie tightened his embrace, resting his head on one of her shoulders. “So, what _really_ happened?”

“Satan’s books…” She answered, tears welling into her eyes. “...were destroyed.”

“All of them?”

“Many of them.”

“Ooh.” Belphie breathed right next to her ear. “He must be feeling terrible right now.” Closing his eyes, he seemed perfectly comfortable in that hug. “…losing something precious is never easy.” His deep voice had that hint of sadness that often inhabited the seventh brother’s words, but he soon dismissed it, getting back to his cozy lazy-self. “Hey, now that Satan doesn’t have a proper room anymore, will you sleep with me?”

Belphegor’s voice was intentionally loud, and that made Satan move in his seat. He got up in a sudden movement, grabbing his bags and motioning in Belphie’s direction. He stopped right by their seat and looked down in a death stare. Satan’s unwavering smile was the worst part of it, as it didn’t seem to reach his eyes. All the wrath he had been containing inside him leaked through his emerald irises, dyeing it with a dangerous red.

“It looks like Lucifer’s dog knows how to growl.” Belphegor whispered with a grin, tightening his embrace around the human girl. She, unaware of the silent battle both brothers had been fighting, averted her eyes to an empty spot in the classroom, thinking that everything that had happened could have been avoided had she kept her mouth shut.

While she mustered enough courage to look Satan in the eyes and ask him for forgiveness, he moved away, leaving the classroom in heavy steps. Belphegor sighed, a bit relieved, and let a small chuckle.

“I… have to go.” She said, realizing that the least she could do was to go and tell him she was sorry. Maybe she could also get some extra books for him to replace the lost ones? Of course, simple books wouldn’t do, but then, perhaps, Simeon could give her some title suggestions? He did offer her his full support when they first met.

Belphegor, who had been staring at her face the whole time, sensed her sudden resolve.

“Belphie?”

“I know you’ll chase Satan if I let you go…” his voice was so deep that she had to twist herself in his even-tighter embrace to make sure that he still was the Belphegor she had known. His purplish eyes sparkled, and a dangerous grin formed over his thin lips. “…that makes me a bit possessive, you know?”

“That sounds fun!” Asmodeus’ voice rang from above, forcing Belphegor to make some room for the fifth brother. “Mind if I join you both?”

“Yuck.” Belphegor scoffed, dodging Asmodeus’s attempt at a group hug.

“You looked so intimate; I couldn’t resist.” He laughed, battling his perfect eyelashes. “You know, with the three of us it could be even funnier!”

“Give me a break.” Belphie stood up steadily, regretfully freeing the human from his embrace. She took this opportunity to bid them goodbye, her heart skipping beats in an unrhythmic pace.

“Belphie was just teasing.” She said to herself, trying to make her breath steady again. “They’re all the same…” And, without looking back, she hurried to the Purgatory Hall dormitory.

**Notes for the Chapter:**

> You knew I'd find an excuse to fit Belphie here.


	3. Afternoon

**Summary for the Chapter:**

> “Do you want these fantasies to be real?”
> 
> “Yes.”
> 
> He choked, taking a step back to his room, and she knew that, once again, he would run away.

Carrying a pile of books, the human girl safely arrived at Satan’s door. Solomon had a bunch of spare titles that would probably interest the fourth brother, so he gave them away in exchange for her promise to come over and try some of his cooking. She agreed to it, unaware of Solomon’s dubious skills in the kitchen.

Placing all the leather covered books on the floor, she originally planned to leave them there and send a message through her D.D.D. asking for Satan’s forgiveness.

“What are you doing?” But his voice startled her before she could finish organizing the books. She jumped back, leaving the last volume unarranged over the pile she had been preparing, and bowed in a hurry.

“I’m sorry for what I said yesterday!” She screamed, panicking. How angry was he? “It wasn’t my intention to offend you or to destroy your collection!” Faced with his silence, she took a deep breath and bowed further. “I-I won’t bother you anymore…!”

“Wait.” Satan gripped one of her wrists before she could run away. His face was stern, no trace of that creepy morning smile anywhere over his lips. Tightening his grip, he pulled her in his direction, gazing deep into her eyes. “Do you really believe in those words?” He asked in a low voice. “Do you believe that I need Lucifer’s permission for every single decision I make?”

She swallowed hard. They were so close that she could feel his breath caressing her skin, inviting her for another of those unfulfilled promises they shared.

“No.” She said, averting her eyes in order to cover for the sudden blush that overtook her. No hope. She wasn't going to fall for his teasings again. “I-it’s my fault for making up fantasies and believing in them.”

Satan gasped, grabbing her other wrist and holding both her arms to get a better look of her expressions.

“I…” She continued, frowning in an attempt to hold the tears that started to form. “I was just frustrated that they weren’t real!”

“But do you want them to be real?”

She stopped, forcing herself to stare him in the eyes. Those deep emerald irises had never looked so serious before, gazing into her soul, forcing her to spill all the truths she hid inside. Satan moved closer, making sure that he was the only thing she could see at that moment. He let her wrists free, moving his hands to cup her face. His touch was gentle, too warm for a demon.

“Yes.”

She said, entrusting herself to his caress. It was Satan’s turn to blush. His eyes went wide, and she knew that, once again, he would run away.

This time, though, Satan took a deep breath and pulled her inside his room, shutting the door with a knock. Part of his library was, indeed, destroyed, but she had no time to check it out. Pushing her against the wall, Satan had pinned her in between his arms, moving until both theirs lips were only inches away. She gasped, too surprised to even react, feeling her heart burst in desynchronized beats.

“I wasn’t waiting for Lucifer’s consent.” He whispered in a smile, nibbling on her ear lobe as he blew these words. “ _I was awaiting yours._ ”


	4. Second Night

**Summary for the Chapter:**

> “Are you sure?” He asked, cheeks red under the frown that covered his face.
> 
> “About what?” Her eyes went wide, and she tightened her hug around his neck.
> 
> “About… this?” Satan blew his words under his breath. “Wrath sometimes hurts.”

First, Satan touched her lips with a soft kiss, melding their mouths into a delicate sight both shared. Then, with the tenderness of a lover, he covered her lower lip in a bite, inviting her to surrender to his plea. She offered no resistance: with parted lips she let him enter, melting under the needy warmth in which he ravaged her mouth. The kiss deepened, and both panted under the excitement of possessing one another.

Pressed against the wall, the human girl had to hug Satan by his neck, seeking support for her almost-numb body. He blushed, suddenly realizing how ridiculously lusty he might have seemed, and separated only enough to look her in the eyes.

“Are you sure?” He asked, cheeks red under the frown that covered his face.

“About what?” Her eyes went wide, and she tightened her hug around his neck.

“About… this?” Satan blew his words under his breath. “Wrath sometimes hurts.”

“Well…” She laughed a bit, smiling back at him. “If it’s you, I’m fine with a little bit of pain.”

“Y-you!” He gasped, grabbing both her hands and holding it against his chest. There, she could feel how fast his heart beat. Satan was too cute for her own good. “Then…” He said, recovering himself with a dangerous glint on his eyes. “…I won’t hold back.”

And he didn’t.

Pressing her against the wall, this time Satan let his hands travel along her body, finding small breaches under her clothes to caress her bare skin. She moaned in his mouth, grabbing the collar of his shirt in a plea for more. Answering, his lips dropped to her neck, where he bit in passionate kisses that would surely leave proofs of their rendezvous. She didn’t complain, though, gasping every time he opened one of the buttons of her uniform to reach another part of her skin. Her coat was gone, and soon was half of her clothes that now laid on the floor where they stood. She did the same to him, taking his shirt off while rubbing her breasts on his chest, humming as he undid the back of her bra. There was a soft “click”, and she wasn’t sure if he had managed to open it or if he had simply broken the clasp in his attempt. She had no time to wonder, as, as soon as her breasts were exposed, he picked her up in a princely gesture and brought her to his purple armchair.

“Say my name.” Satan whispered in a kiss, letting his tongue caress her lips before parting again.

“Satan…?”

She had no time to ask him what he intended to do, as he was quick to spread her legs and, kneeling, to place his mouth right over her panties. He stablished eye contact and, smirking dangerously, he breathed heavily, blowing just enough to make her pant his name in a jerk.

“T-that’s not fair!” She complained, closing her legs in a defensive movement. Satan laughed, placing one of his hands over his chest.

“You’re beautiful.” He chuckled, moving up to trap her in the armchair. “If it’s too much, you just…”

“It’s okay.” She pouted, interrupting him before he could finish his sentence.

“Good.” Satan confessed in a relief, placing both hands on her waist and bending a bit for a quick peck on her lips. “You usually look bewitching in your uniform…” he whispered, nibbling on her ear in a low voice. She gasped, reacting when he traveled down, leaving a wet trace of his tongue against her neck “…but, as you are right now…” Kneeling once again, he let his mouth caress her breasts, using his hands to part her legs once again. She conceded, drowning in the warmth of his fingers as they folded her skirt up, pushing her panties down “…you’re simply…” He looked up, locking eyes with her as he placed his mouth in between her legs. “…irresistible.”

Satan, wetting his lips, let his tongue slide into her folds. She moaned, clutching into the armchair in an attempt to hold the waves of pleasure that ran through her body. Satan groaned, grabbing her by her ass while proving her flavor in circular motions.

“Do not close your eyes.” He mumbled, grabbing her ass even tighter. “Look at me.” And, in a swift movement, he sucked on her clit, toying with it with the tip of his tongue.

“S-Satan!” She moaned, unable to hold the movement of her hips, tensing up as her peak seemed to come. He didn’t bulge, though, using one his hands to make her lay still on the armchair while he kept on sucking on her. She came, maybe one or two times, until he let her go.

“Satan…” She cried in pleasure, extending her wobbly arms in his direction. He answered, enclosing her limp body in a soft hug.

“Yes…?” Satan’s voice was hoarse as he used his only free hand to search for her clit again. She jerked in his arms, feeling how cold his fingers were against her pussy, and instinctively leaned into his touch with a needy whine. “You could ask me anything right now and I’d do it…” He whispered, using his thumb to press her most sensitive part while one of his fingers made its way inside her. “…you look just too cute to be ignored.”

Her inner muscles tightened for the third time that night, enclosing his fingers and trapping it deeper into her. Satan chuckled, noticing how wet she was right now, and she gasped, biting his shoulder in response.

“Ouch!” He said, faking a frown when staring in her eyes. He had removed his hand, using both to hold her at a safe distance from him. “Is that what you wanted to ask for? A bite?”

“N-no…!” She answered in giggles, still numb under the effect of the last orgasm.

“I see…” Satan closed his eyes, nodding to himself. “I’m not one for giving punishments, but…” He stood up, picking her up on his arms and finding his way through the books that cluttered his room. He laid her gently over his bed, holding her chin while she covered her breasts in a self-protective-hug. “…this time you probably deserve it.”

Bracing herself for that little bit of pain she said she would be fine with, the human girl shuddered, closing her eyes in anticipation. But Satan just chuckled, kissing her in tiny pecks that went from her face to her waist. She rolled over the sheets, crinkling her eyes with laughter, too weak to hold anything in. Satisfied with her reaction, Satan then climbed up the bed, pinning her down in between his arms.

“I’ll have to ask you again…” His green eyes were bright as he stared intently down at her, gleaming in the moonlight that made its way through his room. Satan’s golden locks fell in his face, and he brushed it back absently, not even blinking as to not lose sight of her amazed expression. “…do you want to go all the way tonight?”

Amused, she summoned what she had left of strength in her body to leave him a chaste kiss against his lips. Her eyes too, gleamed, filling themselves with his handsome figure.

“I do.”

“Then…” Satan murmured, blushing a bit, the hoarse in his voice sending chills over her body. “…let’s enjoy it together.” With a smirk, he bent down just enough to kiss her, positioning himself over her figure before spreading her legs. He pushed her knees a bit and slid himself into her core, panting all the way down. She jerked, bending into his touch, feeling when her inner walls started to clutch around his hot member. He, too, felt his body a bit numb. The pleasure ran quick in waves, forcing thick drops of sweat to roll under his hair. “I’ll move.” He announced in heavy pants, building up rhythm until her moans became gasps, leaving and entering her body just enough to hear her shudder his name. Satan wanted to smile, but he didn’t even had time to catch his breath before his own body started to change.

Unable to open her eyes, she only felt it when Satan had transformed into his demon form. It was quick, but the pain of his hardened member getting even harder inside her was enough to make her scream. He clutched to her sides, speeding up his thrust, letting his tail tremble when caressing her bottoms. She came once, yanking on his horns in seek of support.

“I’m sorry” she muttered, powerless, sliding her hands back to his hair. He was still moving, the sounds of their overlapping skin filling the bedroom in between the moans both exhaled.

“No.” Satan managed to whisper, using his tail to hold her down by the waist and one hand to twine with her fingers. Covered in sweat, he barely had enough strength to focus his eyes before mumbling: “I’m at my limit.”

He filled her in one intense release, and she wrapped her legs around him, pulling Satan even deeper in an attempt to be completely flooded by him. He couldn’t answer, moaning as relief came through his body.

Exhausted, both laid limp over Satan’s bed. She inhaled deeply: black tea, books, apples and… Satan. His cologne filled her in and out, marking her body with his presence. Sensing her recovery, Satan rolled a bit to her side, diving his nose into her hair and cuddling, embracing her fragile body in a delicate hug. He chuckled once again, satisfied, and left a now chaste kiss against the nape of her neck. She reacted in a low giggle, and he trailed down, passing by her flushed cheeks and covering her still parted mouth.

He would stay by her side for her as long as she desired, loving her for as long as she allowed. Those where the silent promises he would make sure to fulfill.


	5. Morning again

“You look awfully cheerful this morning.” Belphie whimpered, pouting a bit while resting his head on the human’s shoulder. She sat beside him during classes, and he would often take advantage of her “human softness”, as he would call it, to recover from the fatigue that living often imposed him.

“Do I?” She answered, unable to hide the glow of her own smile. Belphegor shut his eyes, blinded by the light she exuded, and sighed next to her ear. She smelled of black tea.

He _hated_ black tea. 

The teacher in front of the class seemed too absorbed in his own subject to even notice their exchange. Satan, sitting in the front roll, also shined, maintaining his perfect posture even straighter than usual.

“Yes.” Belphie mumbled. His hands traveled down to the set of cow-themed pencils Beelzebub had given him. A small bit on one of the tips proved that it was, indeed, a gift of his famished twin brother. “But, don’t worry.” He kept on saying in a low tone, the pout never leaving his lips, the pencils rotating in between his fingers. “…I won’t tell anyone about your fulfilled promises.”

“What?!” She exclaimed, shrinking in her seat when everyone in class turned their heads to stare at her.

Belphegor frowned, pointing out to the bowtie she casually wore that day. No, it wasn’t the usual red ribbon she often wore to classes, but a well-known lime bowtie everyone knew belonged to Satan. The fourth brother seemed to also notice it, suddenly panicking with the fact that he was the one wearing her ribbon.

“It’s okay.” Belphegor said, nifty pulling the bowtie. “You can use mine, instead.” His slender fingers traced the collar of her green shirt and undid it with easiness, placing his blue tie in place. “People may misunderstand…” He grinned, conscious of Satan’s wicked stare, and lowered his voice until it was only a whisper: “…but, at least, no one will know of all the dirty things you did…”

**Notes for the Chapter:**

> That's it! Hope you enjoyed this reading as much as I did while writing it (*•̀ᴗ•́*)و ̑̑  
> And do leave a comment if you liked it! Specially if you intend on praising Belphie. This cutie could always get some more love, hahaha <3


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